Automotive shock absorbers and struts are hydro-mechanical devices employed in vehicle suspension systems designed to isolate the vehicle body from various road inputs and induced vibrations. The shock absorbers and struts provide a damping force against relative motion between the unsprung vehicle wheels and the sprung vehicle body. The damping device generally comprises a rod with a piston slidably engaging a tube assembly. As the rod and piston travel relative to the tube assembly fluid flows through internal valves in a controlled manner. In general, the damping force is a function of the relative velocity between the rod and tube assemblies and the flow restrictions through internal valves.
One known type of valve assembly uses one or more deflective discs made of high strength spring steel seated on an orifice plate to control and restrict flow. The orifice plate has small orifices through which fluid flows during low relative velocity damping events when the discs remain seated against the orifice plate. During mid-range velocity damping events, damping force is determined by the force deflection characteristic of the discs and the resulting flow area. At high velocity, a fixed flow area determines damping force. In some valves the maximum deflection of the discs determines the fixed flow area.
There is often a trade-off between driver comfort during mid-range damping events and disc durability during high velocity events. More particularly, for the disc in the valve to maintain structural integrity during high velocity damping events, the disc deflection must be limited to avoid the possibility of yield of the spring steel or the disc strength must be increased. However, increasing the strength of the disc in the valve often results in increased thickness of the disc and/or its resistance to deflection thereby increasing ride harshness during mid-range events where driver comfort is desired.